Electric heater control



Oct. 28, 1952 P. J. GUILLOT ETAL ELECTRIC HEATER CONTROL Filed June 17, 1949 FIG. 3

Patented Oct. 28, 1952 ELECTRIC HEATER CONTROL Phiiip J. Guillot, Upper Montclair, and Harry R.

Karp, Newark, N. J., assignors to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application June 17, 1949, Serial No. 99,765

(Cl. 21S-20) 4 Claims. 1

The` present application relates to multiple speed gearing and particularly to a novel clutch and gear arrangement for an electric heater control.

An object of the invention is to provide a novel two-speed clutch and gear arrangement for controlling the rate of change in energization of an electric heater for a transparent panel.

Another object is to provide a two-speed solenoid controlled gear train for operating a movable control element so as to vary the rate of change in energization of an electric heater embedded in a transparent panel in response to the temperature appurtenant to the panel.

Another object is to provide a simple, compact two-speed gear train for controlling the rate of application of heat to a transparent panel or Windshield.

Another object of the invention is to provide a novel two-speed control for the application of heat to a windshield.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example.

In the drawing:

Figure 1 is a schematic diagram of a control system for a windshield heater.

Figure 2 is a cross-sectional view of a solenoid operated clutch.

Figure 3 is a sectional view of the clutch of Figure 2 taken in the line 3-3 thereof.

Referring to the drawing of Figure l, there is illustrated a control system for a windshield heater certain features of which Icontrol system have been claimed broadly in application Serial No. 68,594, tiled December 31, 1948, by Joel D. Peterson and other features of which control system have been more specifically disclosed and claimed in application Serial No. 99,764, iiled June 17, 1949, by Harry R. Karp and Allen W. Blanchard. The control system includes an alternator 5 of a suitable type adapted to be driven by an aircraft engine as a source of power, and a variable transformer 1 which is arranged to modify the output voltage applied by the alternator 5 to a windshield heater 9.

The heater 9 of the windshield may be a transparent electrical conductive coating applied to the windshield of a type such as sold under the trade-names Nesa and Electra-Pane. The heater 9 is connected by conductors II and I2 to the output of the transformer 1. The conductor I 2 is connected to a movable arm I3 of the transformer 1. The transformer 'I is connected by conductors I5 and I6 to the output of the alternator 5. The conductor I6 is controlled by onoff switch I1 and limit switch I9 connected in parallel.

A temperature sensing element 2i is embedded in the windshield and comprises a resistance having a high temperature coefficient, such as tungsten, and is used as a master to determine the amount and rate of application of heat to the windshield. The temperature element 2I may be of such a type as shown and claimed in copending application Serial No. 151,009, led March 21, 1950, as a division of the application Serial No. 68,594, iiled December 3l, 1948, by Joel D. Peterson.

The temperature element 2I forms one arm of an alternating current excited bridge 22. A non-thermal sensitive reference resistor 23 serves as another leg of the bridge, and the remaining legs are provided by the windings 24 and 25 forming the secondary of the transformer 26. The bridge circuit is supplied with alternating current by the primary winding 21 inductively coupled 'to the secondary windings 24 and 25. The winding 21 is connected to a suitable source of alternating current. The resistor 23 is of a value such as to balance the bridge when the control temperature, say for example, F. is reached. The output of the bridge will be directional or phased, depending upon whether the resistance of the element 2I Vis above or below the reference resistor 23 which is connected into the bridge by an on-off switch 28 mechanically connected to switch I1. The output voltage of the bridge 22 is connected by conductors 30 and 3| to the input of a phasesensitive detector and amplifier 32.

The output of the amplifier 32 is connected by conductors 33 and 34 to one phase winding of a reversible motor 35, which may be of the two-phase type, the other phase winding being connected by conductors 28A and 29A across the source of alternating current for operation of the motor 35 in a manner well known in the art. The output shaft 35 of the motor 35 is mechanically connected to deliver torque to a gear train 31. The gear train 31 is of a twospeed type having a ratio changing system and solenoid control clutch for selecting output speeds of rotation of N or N/ 10, the operation of which will be explained. 1

The output of the gear train 31 is mechanically connected by a shaft 38 to rotate the movable arm I3 of the variable transformer l to provide an output voltage dependent upon the position of the movable arm. The input voltage of the transformer 'I will be the output voltage of the alternator 5. Thus, when the value of resistor 2| is below that of the resistor 23, the bridge 22 will be unbalanced in a direction to energize the reversible motor 35 so as to drive the movable arm i3 of the transformer 'l in a direction to increase the voltage applied to the windshield Sl. When the value of the resistor ZI is above that of the resistor 23, the bridge 22 will be unbal anced in the opposite direction to energize .the motor 35 so as to drive the movable arm I3 of the transformer 'I in a direction to decrease the voltage applied to the windshield il. Upon the values of the resistors ZI and '23 being equal the bridge will be balanced, hence the motor 35 will not be energized and as long as the temperature of the windshield remains constant, the voltage supplied thereto will be constant. As the temperature changes the control system will con tinuously adjust itself to maintain a constant preselected temperature at the windshield 9 regardless of changes in outside air temperature or heat transfer conditions.

In order to avoid thermal shock or other damage caused by a too rapid change in temperature, it is .necessary to limit the rate of change to a vsafe value when the temperature of the windshield 9 is below a predetermined value, say for example 100 F. However, when the temperature of the windshield Si reaches the predetermined temperature a fast reaction to temperature changes due to changes in outside air temperature, aircraft speed, and heat transfer conditions is desirable. Such a method of applying heat to a transparent panel so as to effect the foregoing is disclosed and claimed in a copending application Serial No. 274,484, yiiled March 1, 1952, by Harry R. Karp and Allen W. Blanchard land assigned to Bendix Aviation Corporation.

By .means o'f 'the two-speed gear train 3l, two 'operating 'speeds are automatically obtained. 'The gear train is mechanically connected to be operated through a solenoid-controlled clutch as will be explained hereinafter with reference to Figures '2 and 3. Control `for the solenoid is provided by an auxiliary circuit ll connected by conductors i3 and Q5 across the output of the bridge 22. The auxiliary circuit II may, for example, be an amplilier circuit so arranged as to have energy iiowing in its output circuit when the temperature of the windshield@ .is belowa predem termined value of, for example 100 F, VA pilot relay winding I is connected by .conductors 4l and 49 across the output of the circuit fil. The relay winding 5I controls an armature element 53 varranged to close switch'contacts 55 upon the winding 5I being energized. Closing the switch contacts 55 energizes the solenoid of the twospeed clutch 3l through conductors 5l and 5B from a D. C. source of electrical energy do.

Upon energization, the solenoid actuates the clutch and thereby the gear train 3l to its N gear ratio Where it will be maintained as long as the control solenoid is energized. When the gear train 3l is in this position, the movable arm I3 of the transformer I will be rotated slowly giving a slow rate of temperature rise.

Upon the temperature of the Windshield 9 reaching 100 F., the auxiliary circuit 4l vcauses relay winding 5I to release the armature 53 under spring tension and return the switch contacts 55 to an open position cle-energizing the control solenoid of the gear train 3l' and return the gear train 37 to its normal N /10 ratio. In this latter position the movable arm I3 will be rotated at a faster rate thus providing fast action to give goed response in the region of the control temperature.

The invention forming the subject matter of the present application is the solenoid controlled clutch gear train assembly 3l illustrated by Figures 2 and 3 and its arrangement and use in the control system heretofore described. 1n the solenoid controlled gear train assembly 3l there is secured to the input shaft 33 a sun gear S3 which meshes wigh planet gears E5, which in tum mesh with orbit gear 5l. The input shaft is rotatably supported housing 59 by bearing ll.

Securely attached to the shaft 3% is a brake plate "53. The planet gears SE are supported on shafts S carried by spiders 'll and is. The spider ll is splined to output shaft 33 which is rotatably supported in the housing by a bearing l2. A compression spring 8l bears against the spider il. Adjacent to the orbit gear El on the housing F52 is a clutch facing S3. A solenoid winding 5E: is arranged around the inner circumference of the housing,T The winding is connected through switch 55 to the source of direct current Si) by two conductors 5l and 59. The orbit gear *El and spider "i8 serve as the armature of the solenoid.

In operation, when the solenoid winding 85 is cle-energized as shown in Figure 2, the spider l is held in intimate contact with the brake plate 'i3 by the pressure of the spring 8l. This locks the planetary system and permits it to rotate with an eifect a direct mechanical connection between the input shaft 3G and output shaft 38 as shown in Figure 2. When the solenoid winding 85 is energized, the pressure of the spring 3l is overcome and the spider I8 is moved out of contact with brake plate 13. Also the orbit gear 5l is biased by the solenoid S5 into intimate contact -with .the brake facing 83 whereupon .the shaft 38 is driven through the planetary gear system.

When the pilot determines that heat will be needed at the windshield 3, he may manually actuate the switch I'I to the on position and close the switch 28 in the bridge circuit 22 so as to place the bridge circuit '22 in an operative condition sensitive to temperature changes. The imbalance inthe bridge circuit 22 causes the solenoid 85 to actuate the gear train 3l to the N ratio. The movable arm I3 Yof the variable transformer operated by the shaft 3B begins to rotate slowly increasing the voltage applied to the windshield 0. As the movable arm I3 moves away from its low voltage position, the limit switch I0 operated by the arm I3 automatically returns to its normally closed position.

When the temperature of the Windshield 9 reaches F. the auxiliary circuit 4I opens the switch 55 and the solenoid 85 becomes de-energized. Spring means 8l actuate the gear train 3l to its N/ l0 ratio so that the arm I3 driven by shaft 38 rotates faster until the temperature is F. As the temperature varies from 120 F., an unbalanced voltage appears at the output of the bridge 22 of Vsuch a phase as to cause the motor 35 to drive the arm I3 in such a direction as to increase (or decrease) the energy supplied and thus maintain 120 F. at the windshield 9.

To shut oli the system, the switch I1 is actuated to its off position. This also opens the interconnected switch 28 in the bridge circuit 22 introducing a large unbalanced voltage in the system of such a phase as to cause motor 35 to drive the arm I3 to a low voltage position. This unbalanced voltage also causes the auxiliary circuit 4I to energize the solenoid 5I and close the switch 55 to energize solenoid 85 which actuates the gear train 31 to its N ratio thereby rotating the arm I3 at a slow rate, thus limiting the rate of decrease of temperature.

Upon the arm I3 reaching its minimum voltage position, it will automatically operate the limit switch I9 to cut off all power to the system. The system will then be in the proper position when it is recycled.

The automatic temperature control system limits the rate of change of temperature to a safe value and also continuously adjusts itself to maintain a constant preselected temperature at the windshield regardless of changes in outside air temperature or heat transfer conditions. The only manual control required is the on-off switch I'I-28 while the novel two-speed control 31 provides automatic means dependent upon conditions affecting the system for varying the rate of temperature change.

Although only one embodiment of the invention has been illustrated and described, various changes in the form anad relative arrangements of the parts may be made to suit requirements.

What is claimed is:

l. For use in a control system for regulating the temperature of a transparent panel having a heater element embodied therein, a temperature sensitive element responsive to the temperature appurtenant to said panel, motor means responsive to said temperature sensitive element, and a movable member for varying the voltage supplied said heater element; a power transmitter comprising an input shaft for connection to said motor means. an output shaft for connection to said movable member, a gear train for interconnecting said shafts, electromagnetic means selectively operable to lock said gear train so as to directly connect in driving relation the input shaft to the output shaft at one speed ratio and to release said locked gear train so as to cause said output shaft to be driven from said input shaft through said gear train at another lower speed ratio, means for electrically connesting said electromagnetic means to said ternperature sensitive element to cause said gear train to eifect said different speed ratios in response to the prevailing temperature appurtenant to the panel.

2. For use in a control system for regulating the temperature of a transparent panel having a heater element embodied therein, a temperature sensitive element responsive to the temperature appurtenant to said panel, motor means responsive to said temperature sensitive element, and a movable member for varying the Voltage supplied said heater element; a power transmitter comprising input shaft for connection to said motor means, an output shaft for connection to said movable member, a gear train for interconneetingsaid shafts, electromagnetic means selectively operable to lock said gear train so as to directly connect in driving relation the input shaft to the output shaft at one speed ratio and to release said locked gear train so as to cause said output shaft to be driven from said input shaft through said gear train at another and lower speed ratio, means for electrically conecti'ng said electromagnetic'means to saidl tem'- perature sensitive element to cause said gear train to effect said different speed ratios in response to the prevailing temperature appurtenant to the panel, said gear train including a planetary gear train connectingv the input Land output shafts, spring means for biasing said gear train in one position to lock said gear train, and said planetary gear train biased by said electromagnetic means to a second position against the bias of said spring means so as to cause said gear train to be operative at predetermined temperature conditions appurtenant to the panel.

3. For use in a control system for regulating the temperature of a transparent panel having a heater element embodied therein, a tempera"- ture sensitive element responsive to the temperature appurtenant to said panel, motor means responsive to said temperature sensitive element, and a movable member for varying the voltage supplied said heater element; a, power transmitter comprising an input shaft for connection to said motor means, an output shaft for connection to said movable member, a gear train for interconnecting said shafts, electromagnetic means selectively operable to lock said gear train so as to directly connect in driving relation the input shaft to the output shaft at one speed ratio and to release said locked gear train so as to permit said output shaft to be driven from said input shaft through said gear train at another and lower speed ratio, means for electrically connecting said electromagnetic means to said temperature sensitive element to cause said gear train to effect said different speed ratios in response to the prevailing temperature appurtenant to the panel, said gear train including a planetary gear train having a sun gear, a plurality of planet gears, and an orbit gear, first means for locking the planetary gear train for effecting a direct mechanical connection between said input and output shafts, and second means operated by the electromagnetic means for overcoming said first means and to lock said orbit gear to effect power transmission from said input shaft to said output shaft through said planetary gear train at a lower speed ratio upon the temperature appurtenant to the panel being below a predetermined value.

4. For use in a control system for regulating the temperature of a windshield having a heater element embodied therein, the combination of a two-speed power transmitting device having an input shaft, an output shaft, a planetary gear train interconnecting said shafts, said gear train having a sun gear, a plurality of planet gears, a planet gear cage and an orbit gear, a releasable clutch for drivingly connecting said input and output shafts, means for normally biasing said planet gear cage into engaging relation with said clutch for rotation of said output shaft directly with said input shaft, a solenoid winding circumferential of said orbit gear, engageable brake means for said orbit gear controlled by the solenoid winding, means for supplying electrical energy to said windshield including a movable arm for varying the voltage thereof, said movable arm operatively connected for actuation by the output shaft, a temperature sensitive element responsive to the temperature appurtenant to said windshield, motor means responsive to said temperature sensitive element for driving said input shaft in a direction so as to maintain the temperature of said windshield at a predetermined temperature, and means in- 7 cludig said temperature element for energizing said solenoid Winding upon a predetermined temperature condition to overcome saidy biasing means to cause said clutch to release said planet gear cage and said brake means to engage said 5 orbit' gear so as to cause said output shaft to be rotated through said gear train by the input shaft at a relatively slow rate and thereby to control the rate of temperature change.

PHILIP J. GUILLOT. 10

HARRY R. KARP.

REFERENCES CITED .y The following references are of record in the 15 file-o1'v this patent:

Numb

Number 8 UNITED STATES PATENTS- Name Date Tompkins July'S, 1928 Hull Dec. 4, 1928 Gano June 4, 1929 Whitman Jan. 9', 1934 Wilhjelm May 4, 1937 Mershon Feb. 22, 1949 Mersh'on May 17, 1949 FOREIGN PATENTS Country Date Germany July 23, 1924 France June 21, 1922 France Mar. 8, 1925 France July 5,v 1937 

